Due to problems with waste water treatment, acidic liquid cleaners for aluminum are currently being converted from the fluorine-based cleaners used heretofore to fluorine-free, chromium-free cleaners.
The acidic liquid aluminum cleaners disclosed in, for example, (a) Japanese Patent Application Laid Open [Kokai] Number 61-106783 [106,783/86], (b) Japanese Patent Application Laid Open Number 61-231188 [231,188/86], and (c) Japanese Patent Application Laid Open Number HEI 2-73983 [73,983] are examples of prior art fluorine-free, chromium-free cleaners. The liquid cleaners disclosed in (a) and (b) are sulfuric acid-based acidic liquid cleaners for aluminum. In addition to sulfuric acid, nitric acid, and surfactant, these also contain ferric ion (etching accelerator) and an oxidant (stabilizer for the ferric ion). These compositions are heated to 50.degree. to 80.degree. C. for use in cleaning. The liquid cleaner in (c) is a phosphoric acid-based acidic liquid cleaner for aluminum. In addition to phosphoric acid, sulfuric acid, and surfactant, it contains small amounts of ferric ion (in order to inhibit corrosion of the cleaning equipment) and an oxidant which acts as a stabilizer for the ferric ion. It is heated to 50.degree. to 80.degree. C. for use in cleaning.